Network Working Group                                   Aaron Stone, Ed.

Internet-Draft                                           Six Apart, Ltd.

Intended status: Informational                         December 14, 2007

Expires: June 16, 2008

              Memcache Binary Protocol: Extensions for UDP

                      draft-stone-memcache-udp-01

Abstract

   This memo explains extensions to the memcache binary protocol for use

   in a UDP environment.

   Memcache is a high performance key-value cache.  It is intentionally

   a dumb cache, optimized for speed only.  Applications using memcache

   do not rely on it for data -- a persistent database with guaranteed

   reliability is strongly recommended -- but applications can run much

   faster when cached data is available in memcache.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the

   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering

   Task Force (IETF).  Note that other groups may also distribute

   working documents as Internet-Drafts.  The list of current Internet-

   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months

   and may be updated, replaced, or obsoleted by other documents at any

   time.  It is inappropriate to use Internet-Drafts as reference

   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 16, 2008.

Copyright Notice

   Copyright (c) 2007 IETF Trust and the persons identified as the

   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal

   Provisions Relating to IETF Documents

   (http://trustee.ietf.org/license-info) in effect on the date of

   publication of this document.  Please review these documents

   carefully, as they describe your rights and restrictions with respect

   to this document.  Code Components extracted from this document must

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   include Simplified BSD License text as described in Section 4.e of

   the Trust Legal Provisions and are provided without warranty as

   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2

     1.1.  Conventions Used In This Document . . . . . . . . . . . .   2

   2.  Defined Values  . . . . . . . . . . . . . . . . . . . . . . .   3

     2.1.  Magic Byte  . . . . . . . . . . . . . . . . . . . . . . .   3

     2.2.  Response Status . . . . . . . . . . . . . . . . . . . . .   3

     2.3.  Command Opcodes . . . . . . . . . . . . . . . . . . . . .   3

     2.4.  Data Types  . . . . . . . . . . . . . . . . . . . . . . .   3

   3.  Commands  . . . . . . . . . . . . . . . . . . . . . . . . . .   3

     3.1.  Get Response  . . . . . . . . . . . . . . . . . . . . . .   3

     3.2.  Get Range Request . . . . . . . . . . . . . . . . . . . .   4

     3.3.  Get Range Response  . . . . . . . . . . . . . . . . . . .   4

   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5

   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   5

   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Memcache is a high performance key-value cache.  It is intentionally

   a dumb cache, optimized for speed only.  Applications using memcache

   do not rely on it for data -- a persistent database with guaranteed

   reliability is strongly recommended -- but applications can run much

   faster when cached data is available in memcache.

   Sites may find that, due to their network architecture or application

   usage patterns, the stateless [UDP] protocol better suits their

   needs.  This document provides extensions and descriptions of use of

   the memcache protocol [MEMCACHE] in a UDP environment.

   It is a goal of this document to provide sufficient information in

   each UDP packet as to avoid any requirement for statefulness on the

   part of the server nor significant caching of outstanding packets on

   the part of the client.

1.1.  Conventions Used In This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

   document are to be interpreted as described in [KEYWORDS].

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2.  Defined Values

2.1.  Magic Byte

   The magic bytes remains the same as in [MEMCACHE].

2.2.  Response Status

   Additional status values:

   0x0004  Value is larger than a single response packet

2.3.  Command Opcodes

   Additional opcode values:

   0x0C    Get Range

   0x0D    Set Range

2.4.  Data Types

   There are no new data types in this extension.

3.  Commands

3.1.  Get Response

   This section extends the behavior of the Get and GetQ commands as

   described in [MEMCACHE].

   When a Get or GetQ request is made via UDP, and the value of the key

   for which the request was made is larger than can be placed into a

   single UDP packet (noting that the protocol header must also be

   counted), a Get Range response packet MUST be sent instead of the Get

   response packet.  In this instance:

   1.  The Status field of the response header MUST be 0x0004.

   2.  The Offset field of the GetR response extras MUST be 0.

   3.  The Length field of the GetR response extras, and the data

       contained in the Value field of the packet, SHOULD be the maximum

       allowed length of a UDP packet, less the space required by the

       header and extras; however it MAY be any amount below this

       maximum.

   4.  The Total value length field of the response extras MUST be the

       actual length of the complete value.

   The client, upon receipt of a Get Range response bearing Status 0x004

   and a Message ID corresponding to its Get request, shall then know

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   that it has received only the first portion of the value.  The client

   MAY choose to request the remaining portion of the value by sending

   one or more Get Range requests.

3.2.  Get Range Request

   The Get Range request is primarily intended for use over a UDP

   transport to request byte ranges of the value for a key.  In the

   event that the Data version check fails to match that of the key, an

   error MUST be returned.

   Extra data for get range request:

   Byte/     0       |       1       |       2       |       3       |

      /              |               |               |               |

     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|

     +---------------+---------------+---------------+---------------+

    0| Flags                                                         |

     +---------------+---------------+---------------+---------------+

    4| Data version check                                            |

     |                                                               |

     +---------------+---------------+---------------+---------------+

   12| Offset                                                        |

     +---------------+---------------+---------------+---------------+

   16| Length                                                        |

     +---------------+---------------+---------------+---------------+

   Total 20 bytes

3.3.  Get Range Response

   The Get Range request is primarily intended for use over a UDP

   transport to indicate the location of the bytes of the value for a

   key contained in a given packet.  A client receives enough

   information in each Get Range extras to construct an appropriately

   sized buffer in its own memory and blindly insert the contents of the

   packet at the given byte offset.

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   Extra data for get range response:

   Byte/     0       |       1       |       2       |       3       |

      /              |               |               |               |

     |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|

     +---------------+---------------+---------------+---------------+

    0| Flags                                                         |

     +---------------+---------------+---------------+---------------+

    4| Data version check                                            |

     |                                                               |

     +---------------+---------------+---------------+---------------+

   12| Offset                                                        |

     +---------------+---------------+---------------+---------------+

   16| Length                                                        |

     +---------------+---------------+---------------+---------------+

   20| Total value length                                            |

     +---------------+---------------+---------------+---------------+

   Total 24 bytes

4.  Security Considerations

   This document does not introduce any new security considerations

   beyond those discussed in [MEMCACHE].

5.  Normative References

   [KEYWORDS]

              Bradner, S., "Key words for use in RFCs to Indicate

              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [MEMCACHE]

              Bradner, S., "Key words for use in RFCs to Indicate

              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [UDP]      Postel, J., "User Datagram Protocol", STD 6, RFC 768,

              August 1980.

Author's Address

   Aaron Stone (editor)

   Six Apart, Ltd.

   548 4th Street

   San Francisco, CA  94107

   USA

   Email: aaron@serendipity.palo-alto.ca.us

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